Exploring the Global.asax file in ASP.NET

Abstract: Have you ever felt the need of writing logic at the application level; precisely a location or a file where you could handle events or errors at the application level? Well if yes, then enter the Global.asax. Using this file, you can define event handlers with application-wide or session-wide scope. In this article, we will explore the application and session level events exposed in the Global.asax file and how we can utilize these events in our applications.

Exploring the Global.asax file in ASP.NET

Have you ever felt the need of writing logic at the application level; precisely a location or a file where you could handle events or errors at the application level? Well if yes, then enter the Global.asax. Using this file, you can define event handlers with application-wide or session-wide scope. In this article, we will explore the application and session level events exposed in the Global.asax file and how we can utilize these events in our applications.

The Global.asax, also known as the ASP.NET application file, is located in the root directory of an ASP.NET application. This file contains code that is executed in response to application-level and session-level events raised by ASP.NET or by HTTP modules. You can also define ‘objects’ with application-wide or session-wide scope in the Global.asax file. These events and objects declared in the Global.asax are applied to all resources in that web application.

Note 1: The Global.asax is an optional file. Use it only when there is a need for it.

Note 2: If a user requests the Global.asax file, the request is rejected. External users cannot view the file.

The Global.asax file is parsed and dynamically compiled by ASP.NET. You can deploy this file as an assembly in the \bin directory of an ASP.NET application.

There are 2 ‘set’ of methods that fire corresponding to the events. The first set which gets invoked on each request and the second set which does not get invoked on each request. Let us explore these methods.

Methods corresponding to events that fire on each request

Application_BeginRequest() – fired when a request for the web application comes in.

Application_AuthenticateRequest –fired just before the user credentials are authenticated. You can specify your own authentication logic over here.

Application_AuthorizeRequest() – fired on successful authentication of user’s credentials. You can use this method to give authorization rights to user.

Application_ResolveRequestCache() – fired on successful completion of an authorization request.

Application_AcquireRequestState() – fired just before the session state is retrieved for the current request.

Application_PreRequestHandlerExecute() - fired before the page framework begins before executing an event handler to handle the request.

Application_PostRequestHandlerExecute() – fired after HTTP handler has executed the request.

Application_ReleaseRequestState() – fired before current state data kept in the session collection is serialized.

Application_UpdateRequestCache() – fired before information is added to output cache of the page.

Application_EndRequest() – fired at the end of each request

Methods corresponding to events that do not fire on each request

Application_Start() – fired when the first resource is requested from the web server and the web application starts.

Session_Start() – fired when session starts on each new user requesting a page.

Application_Error() – fired when an error occurs.

Session_End() – fired when the session of a user ends.

Application_End() – fired when the web application ends.

Application_Disposed() - fired when the web application is destroyed.

Show me an example!!

Let us see an example of how to use the Global.asax to catch unhandled errors that occur at the application level.

To catch unhandled errors, do the following. Add a Global.asax file (Right click project > Add New Item > Global.asax). In the Application_Error() method, add the following code:

Suprotim has received the prestigious Microsoft MVP award for nine times in a row now. In a professional capacity, he is the CEO of A2Z Knowledge Visuals Pvt Ltd, a digital group that represents premium web sites and digital publications comprising of Professional web, windows, mobile and cloud developers, technical managers, and architects.

This is very nice example mention my you, this is helpful for programming logic.
Thanks
Shakti
<strong><a href="http://www.nextmvp.blogspot.com/" >www.nextmvp.blogspot.com</a></strong>

Comment posted by
Thanigainathan
on Friday, January 9, 2009 4:55 AM

Hi,

This article is nice. But have not mentioned any specific usage of Global.asax in page level.
Please give some example in that.

Thanks,
Thani

Comment posted by
Song
on Friday, January 9, 2009 12:16 PM

example is good, but if show how to show on .aspx page the err, it were more better

Comment posted by
srikanth
on Friday, January 9, 2009 4:32 PM

I think app_error will not be called if u install your app on IIS and if any un-handled exception is called...
this is what i am experiencing right now in my app.
can you confirm whether app_error in global.asax is called if i install it on IIS???
mine is asp.net 2.0 app

Comment posted by
Jigar
on Monday, January 12, 2009 1:04 AM

This is a good article but there is no option on the page to print this article as it is.

Comment posted by
vineet kumar
on Tuesday, April 7, 2009 1:55 AM

This is a good article regarding global.asax.
i have searched a lot about this file and its events, but hardly get something usefull. Can u please tell me how to use response.redirect() method in global.asax file. Can we use javascript in this file. Actually i want the reference of the current httprequest in global.asax whenever any event of this file is fired. Can u tell me that whether its possible or not. Thanks

Comment posted by
Waqar Ahmad
on Wednesday, May 13, 2009 3:10 AM

Great Article thanx

Comment posted by
Adam
on Friday, September 11, 2009 4:55 PM

this article is very nice but we need to more examples to handel it

Comment posted by
satish
on Monday, November 9, 2009 10:45 AM

It's good Articles , but something is missed, over all that good statement

Hey man....
This is the best article till now i have seen about global.asax, described in quite a simple way..
but can you please tell me where can i get much more advanced infor about this global fine.

Comment posted by
prajakta
on Friday, March 4, 2011 7:11 AM

Nice article.
But I have one question : When I browse my application, Application_BeginRequest() event will get fired. But what if I close the browser itself? None of the event is fired in this case. In this case when the Session_End() event will get fired?

Thanks.

Comment posted by
billu
on Monday, March 21, 2011 3:12 AM

example not enough

Comment posted by
Perumal
on Monday, July 18, 2011 9:53 AM

Simple & Clear explanations.
thanks suprotim

Comment posted by
hi
on Monday, December 12, 2011 6:12 AM

fhgfdh

Comment posted by
s
on Tuesday, April 24, 2012 4:03 AM

s

Comment posted by
remo
on Thursday, May 10, 2012 6:09 AM

Very good example...

Comment posted by
kumar
on Tuesday, June 12, 2012 4:42 AM

nice post

Comment posted by
mike
on Tuesday, June 12, 2012 4:43 AM

you may like this post:
http://webgeek.elletis.com/how-to-create-global-functions-in-asp-net-4-0/

Comment posted by
Vijay
on Thursday, August 29, 2013 4:02 AM

Informative.. Thanks for the post.. :)

Comment posted by
swapna
on Friday, June 6, 2014 6:43 AM

how to add Application_OnPostRequestHandlerExecute()in global.asax programmatically??